According to the kind defined in detail in the preamble of claim 1, the invention relates to a method for control of an automatic transmission of a motor vehicle having an electronic gear control which continuously exchanges signals with at least one vehicle dynamics regulator.
The use of the intelligence in electronics is illustrated in motor vehicles with automatic transmissions by application of an electronic gear control (EGS) with which criteria known to be relevant for the customers, such as driving comfort and driveability and also criteria relevant to safety, are met to a great extent.
For automatic selection of shift program stored in the electronic gear control which describes, for ex., a known driver type recognition, an environment recognition, a driving situation recognition, or a manual engagement recognition, known from the publication xe2x80x9cATZ Automobiltechnische Zeitschriftxe2x80x9d 94 (1992) and for gear selection according to situations, the electronic gear control continuously communicates with other control units and computers of different aggregates via a CAN data bus (Controlled Area Network).
It is known from the practice that the electronic gear control is linked with a vehicle dynamics regulator (FDR) which coordinates and assists with different regulation systems in the braking system and in the drive train. Belonging to the output signals of this regulation system are, for ex., an anti-blocking system (ABS) against blockage of the wheels when braking, an anti-slip control system (ASC) against spinning of the wheels when driving and an engine management that regulates the engagement in the engine control, are issued via the vehicle dynamics regulator to the electronic gear control.
The operating mode of an anti-slip control system has been disclosed, for ex., in DE 34 35 869 A1 and EP 0 583 610 B1.
In these input slip regulation systems known already, in the case of a spinning tendency at least one driven wheel reduces the engine torque and, at the same time, produces a control signal which is passed on to the electronic gear control of an automatic transmission at the start of the engine torque reduction. On the strength of that the electronic gear control introduces a shift to the higher gear.
In addition, in EP 0 583 610 B1 has in addition been described a so-called xe2x80x9cwinter programxe2x80x9d in which, according to a regulating signal of the anti-slip control system, a shift program is started with output-torque reducing shift characteristic lines until an interruption criterion is met.
Together with a vehicle dynamic control with an anti-slip control system and an anti-blocking system, a special program showing a dynamic stabilizer (DS) is known from the practice. The system brakes certain wheels, for ex., upon a critical transverse acceleration of the vehicle, in order to prevent a lateral jack-knifing of the vehicle.
However, the gear control methods known already prove insufficient in some special operating situations.
One of these special operating situation occurs, for ex., when the vehicle dynamics control, on the basis of a signal of the anti-slip control system or of the anti-blocking system, calls for a special driving program with gear shifts in the electronic gear control while a situation is detected by the dynamic stabilizer which requires prevention of the gear shift.
As result of the insufficient assistance of the dynamics stabilizer by the electronic gear control, it is possible for load changes to be carried out which impair the driving comfort and under certain circumstances further destabilize the existing insecure driving state.
The problem on which this invention is based is to make available a method for control of an automatic transmission having an electronic gear control which communicates with a vehicle dynamics control and with a view to better driving comfort and increased safety, can equally react to a signal of an anti-slip control system or of an anti-blocking system, the same as to a signal of a dynamic stabilizer.
By means of the inventive method in which the dynamic stabilizer DS is integrated in the regulation system of the vehicle dynamics regulator FDR and a signal of the dynamic stabilizer DS is processed simultaneously with a signal of the anti-slip control system ASC and/or of the anti-blocking system ABS entering into the electronic gear control EGS, the electronic gear control reacts supportingly in the same manner to the dynamic stabilizer and to the anti-slip control system or anti-blocking system.
The vehicle dynamics regulator offers during slip detection for ex., a change to a special drive program which contains all the shift characteristic lines and converter characteristic lines for a drive mode preventive of slip. The output-put torque reducing shift characteristic lines of this drive program should prevent, or at least reduce, slip on a road having a low frictional value.
Besides, the vehicle dynamics regulator FDR offers the possibility of triggering shifting preventions when thereby the dynamic stabilizer DS is assisted.
When the vehicle dynamics regulator FDR detects during a dynamic stabilization DS that a certain criterion such as, for ex., too high a transverse acceleration has been met, the electronic gear control is engaged, via a corresponding signal, for preventing gear shifts and if needed a deceleration of certain wheels is called for in order to ensure stability of the vehicle.
Since via a function stored in the electronic gear EGS, in addition to the processing of the signal of the anti-slip control system ASC or of the anti-blocking system ABS, it is now at the same time reacted also to a signal of the vehicle dynamics regulator FDR to prevent gear shifts and on the gear side the special conditions of the vehicle dynamics control are taken into account, with the inventive method this represents a gear-assisted dynamic stabilization for the vehicle.